Threats / Cisco / CVE-2020-3118
CVE-2020-3118
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Cisco IOS XR vulnerability
Cisco IOS XR improperly validates string input in Cisco Discovery Protocol messages, allowing unauthenticated adjacent attackers to execute administrative code or trigger device reload.
Verdict
Today item — known-exploited.
An adjacent attacker without credentials can exploit improper input validation in CDP messages to achieve remote code execution with administrative privileges or cause denial of service through device reload on affected IOS XR systems.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
4 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.11806 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Cisco, IOS XR. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-134 Format String.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
WeaknessCWE-134 · Format String
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious Cisco Discovery Protocol message with improperly validated string input and send it to an adjacent network segment.
Business
Network infrastructure loses availability or is compromised with administrative access, disrupting operations and enabling lateral movement.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit the format string vulnerability to execute arbitrary code with the privileges of the routing device.
Business
Attackers gain control of critical network infrastructure, potentially exfiltrating data or redirecting traffic.
3
Lateral reach — past segmentation narrative 3
Attacker
I trigger a device reload through the same vulnerability to cause immediate service disruption.
Business
Network outage impacts business continuity and customer-facing services dependent on that infrastructure.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05